Japanese-name sibling to Vesper?

Our daughter, VesperElizabeth will have a sibling in a little under 6 months from now. We are tossing around a lot of names (and we won't be finding out the gender) but I'm trying to see if any Japanese names will fit. Neither my husband nor I are Japanese but we have been living in Japan for the 2.5 years since my daughter was born and will be there for the birth of our next child.

Can you think of any way I can have a sibset and use a name from the country where our child will be born? We have a hyphenated last name with an English and Polish name.

-Rin is said REEN, rhyming with lean or keen. Ren would rhyme with Wren.
-Sara is said saw-ruh, not Sare-uh
-Ami is ah-mi not Amy
-Erika is eh-rlee-kuh, with the weird twist on the 'r'.

Seeing you live in Japan, you probably already know this, but here is a basic guide to vowel sounds with their Romaji (English alphabet) equivalent:

A is said 'ah' as in odd or car
E is said 'eh' as in elk or Ella
I is said 'ee' as in me or see
O is said 'oh' as in own or Joe
U is said 'ooh' as in boo or soon- but is often barely heard and very short.

Also, although Japan doesn't have an official popularity list, many Japanese parenting sites have polls that give a fairly accurate representation of name popularity.

One important thing to note about Japanese names is that many of them are truly unisex. There are also a lot of base 'names' that have different prefixes or suffixes that change the meaning.

For example, take Katsu. It's a boys' name meaning victory.

By adding the character for 'ki', you get Katsuki, which roughly translates to 'strength of victory'. Ki is predominantly a boys' ending.
By adding the character 'mi', you get Katsumi, which roughly translates to 'beautiful victory'. Mi is almost exclusively a girls' suffix (it can be a prefix, but more commonly is added at the end.)

How long are you planning to live in Japan? VesperElizabeth is not a very Japanese-friendly name; I bet Vesper comes out as Besupa. If you are in the military and will be traveling a lot, than I suggest a name easy to say English and Japanese, but not necessarily Japanese, such as: